Why Sitting May Be Bad for Your Brain

Why Sitting May Be Bad for Your Brain – By Gretchen Reynolds – Aug. 15, 2018

Sitting for hours without moving can slow the flow of blood to our brains, according to a cautionary new study of office workers, a finding that could have implications for long-term brain health.

But getting up and strolling for just two minutes every half-hour seems to stave off this decline in brain blood flow and may even increase it.

That sounds so reasonable and almost trivial until you try it yourself.  

Then you discover how unproductive you become when you’re interrupted every half hour in the middle of reading, writing, constructing, or even cleaning.

Any activity that requires your sustained mental and physical resources, even briefly, cannot just be stopped and restarted without time-consuming consequences.

Delivering blood to our brains is one of those automatic internal processes that most of us seldom consider, although it is essential for life and cognition. Brain cells need the oxygen and nutrients that blood contains, and several large arteries constantly shuttle blood up to our skulls.

Because this flow is so necessary, the brain tightly regulates it, tracking a variety of physiological signals, including the levels of carbon dioxide in our blood, to keep the flow rate within a very narrow range.

But small fluctuations do occur, both sudden and lingering, and may have repercussions.

Past studies in people and animals indicate that slight, short-term drops in brain blood flow can temporarily cloud thinking and memory, while longer-term declines are linked to higher risks for some neurodegenerative diseases, including dementia.

Other research has shown that uninterrupted sitting dampens blood flow to various parts of the body.

I believe that’s something I can feel after I’ve been sitting too long (ignoring my computer’s regularly scheduled exercise alarms). I can certainly feel the blood pooled in my lower legs but I assume that’s due to my overly-elastic EDS tissue making vein walls stretch and bulge.

Whether a similar decline might occur in the arteries carrying blood to our brains was not known, however.

So for the new study, which was published in June in the Journal of Applied Physiology, researchers at Liverpool John Moores University in England gathered 15 healthy, adult, male and female office workers.

That’s certainly not an impressive number.

The researchers asked these men and women to visit the university’s performance lab on three separate occasions. During each, they were fitted with specialized headbands containing ultrasound probes that would track blood flow through their middle cerebral arteries, one of the main vessels supplying blood to the brain.

They also breathed briefly into masks that measured their carbon dioxide levels at the start of the session, so that scientists could see whether levels of that gas might be driving changes in brain blood flow. Blood carbon dioxide levels can be altered by changes in breathing, among many other factors.

Then the men and women spent four hours simulating office time, sitting at a desk and reading or working at a computer.

During another visit, they were directed to get up every 30 minutes and move onto a treadmill set up next to their desks. They then walked for two minutes at whatever pace felt comfortable, with an average, leisurely speed of about two miles an hour.

In a final session, they left their chairs only after two hours, but then walked on the treadmills for eight minutes at the same gentle pace.

As they had expected, brain blood flow dropped when people sat for four continuous hours. The decline was small but noticeable by the end of the session.

It was equally apparent when people broke up their sitting after two hours, although blood flow rose during the actual walking break. It soon sank again, the ultrasound probes showed, and was lower at the end of that session than at its start.

But brain blood flow rose slightly when the four hours included frequent, two-minute walking breaks, the scientists found.

Interestingly, none of these changes in brain blood flow were dictated by alterations in breathing and carbon dioxide levels, the scientists also determined. Carbon dioxide levels had remained steady before and after each session.

So something else about sitting and moving was affecting the movement of blood to the brain.

[the study] was not designed to tell us whether any impacts on the brain from hours of sitting could accumulate over time or if they are transitory and wiped away once we finally do get up from our desks for the day.

the results do provide one more reason to avoid sitting for long, uninterrupted stretches of time,

They also offer the helpful information that breaks can be short but should be recurrent.

“Only the frequent two-minute walking breaks had an overall effect of preventing a decline in brain blood flow,” she says.

So consider setting your computer or phone to beep at you every half-hour and get up then, she suggests.

I’ve done that and it works very well…. if you actually take the breaks :-)

My computer app, Workrave, does an excellent job at calculating your time steadily working/sitting, has 3 different levels of alarm duration, and the alarms are fully configurable.

WorkRave: PC App to enforce breaks at computer

My excuse for not following the alarms is that my thinking process is so fragile that it would be derailed by taking a break before I’ve finished writing it down. But each day, I start with good intentions and I do get in a few breaks “suggested” by the app that I wouldn’t have otherwise.

Stroll down the hall, take the stairs to visit a restroom a floor above or below your own, or complete a few easy laps around your office.

Your brain just might thank you years from now, when you’re no longer tied to that office chair.

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